I would also like this but wanted to point out that the method you mention that does create a tablebox with a colored cell is broken if the table box is then sorted with "Sort by Column". below, the table at first had Jane's height highlighted in row 3 but after sorting by name now it's Susan's height that is highlighted, because it's what's in row 3.
I'm having various issues with the possibility that a user might sort a tablebox I've created with JSL by using Sort by Column. I just learned that before JMP16.2 the contents of a Colbox in a table box do not sort at all and in 16.2 where they do sort in the UI those display tree elements don't rearrange (if in the above tablebox name were a Colbox of textboxes instead of a stringcolbox, the textbox with "JUDY" in it would still be textbox(3) even after the table was sorted). Giving the various column boxes one or more "properties" lists that would sort just like the values lists do for stringcolbox and numcolbox, and similarly accessible and settable with get and set functions, would be a way to allow individual cell colors (and more formatting) and such a list for a colbox could reveal the current box positions - if there is some obstacle to actually reordering the display tree for the colbox.